2P Imaging and Dendritic-Synaptic Physiology In order for the brain and peripheral nervous system to work properly, neurons must communicate effectively with one another. This communication is accomplished at specialized structures called synapses. The vast majority of synaptic contacts are made on neuronal dendrites. Synaptic complexes found in dendrites are complex transduction machines created by a partnership between pre- and postsynaptic cells. The dendritic membrane outside of the synaptic specialization is also a highly specialized, dynamic structure that is richly invested with voltage-dependent ion channels, G-protein coupled receptors, signaling enzymes, translational and protein processing machinery. Fundamental insights into the roles of dendrites in health and disease are emerging from our ability to visualize these microscopic regions dynamically in living tissue. NU is rapidly becoming a world center in the study of dendrites and synaptic function. The NU group was nucleated by the recruitment of Drs. Nelson Spruston and Catherine Wooley, internationally recognized leaders in the study of neuronal dendrites. In 2001, Dr. James Surmeier was recruited to the Chair of the Physiology Department at FSM. Having a well-established reputation for the study of neuromodulatory mechanisms that are critical to dendritic function in neurons, he put in motion a strategic plan to dramatically expand the group of neuroscientists working in this area at NU. This decision was predicated upon 1) existing strengths in this area, 2) the recognition that this was an emerging area of neuroscience and 3) the conviction that a wide array of major neurological disorders - Parkinson's disease, Alzheimer's disease, neuropsychiatric disorders, and drug abuse - were likely to be primarily disorders of dendrites and synaptic function. With the recruitment of twelve new faculty members into this area in the last three years, this group has achieved a critical mass. Even though the recruitment has focused heavily on junior investigators (because this is an emerging area of neuroscience), the group is already very well funded by NIH, receiving roughly $12M in 2004-05, of which $XM is derived from NINDS. This figure is sure to grow as many of the young recruits with 2P expertise (e.g., P. Osten, J. Waters, G. Shepherd) are submitting their first grants to NINDS this year. Collectively, this group represents one of the largest and most experienced collections of physiologists pursuing dendritic and synaptic physiology in the world (Table 1A). Most are experienced electrophysiologists, and several are experts at electrical recording from dendrites (Spruston, Maccaferri, Martina, Waters, Osten). Several are experts at using optical methods for studying dendritic properties (Hockberger, Spruston, Grutzendler, Shepherd, Penzes, Waters, Osten). Others are currently developing this expertise (Surmeier, Bevan, Mintz, Martina, Singer) with publications beginning to appear in this area (e.g., Surmeier's lab: Day et al., Nature Neuroscience, Feb. 2006). Most of the investigators are in the same department (Physiology) where they have the opportunity to interact with one another on a daily basis. Most of those who are in the Ophthalmology and Neurology departments have adjacent labs. Surmeier, Miller, Rao and Bevan are in one large open lab space. The contiguity of most of the participating faculty creates a unique opportunity for crossfertilization of ideas and collaborations. Because each of these investigators is posing important questions about dendrites and synapses, a clear obstacle to maximizing the yield on the NINDS and NU investment in them is their limited access to non-linear optical technology. In the last three years, NU has taken steps to correct this limitation by making a major investment in space, equipment and personnel. This proposal aims to build upon this investment to make this technology available to investigators throughout NU.